Bonded abrasive article and method of forming

ABSTRACT

An abrasive article includes a body having abrasive grains contained within a bond material comprising a metal or metal alloy, wherein the body comprises a ratio of V AG /V BM  of at least about 1.3, wherein V AG  is the volume percent of abrasive grains within the total volume of the body and V BM  is the volume percent of bond material within the total volume of the body.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority under 35 U.S.C. §120 to and is acontinuation of U.S. application Ser. No. 13/225,114 entitled “BondedAbrasive Article and Method of Forming,” by Srinivasan Ramanath, et al.,filed Sep. 2, 2011, which in turn claims priority from U.S. ProvisionalPatent Application No. 61/379,920, filed Sep. 3, 2010, entitled “BondedAbrasive Article and Method of Forming”, naming inventors SrinivasanRamanath, et al., which application is incorporated by reference hereinin its entirety.

BACKGROUND

1. Field of the Disclosure

The following is directed bonded abrasive articles, and moreparticularly, bonded abrasive articles including abrasive grainscontained within a bond material including a metal or metal alloy.

2. Description of the Related Art

Abrasives used in machining applications typically include bondedabrasive articles and coated abrasive articles. Coated abrasive articlesare generally layered articles having a backing and an adhesive coat tofix abrasive grains to the backing, the most common example of which issandpaper. Bonded abrasive tools consist of rigid, and typicallymonolithic, three-dimensional, abrasive composites in the form ofwheels, discs, segments, mounted points, hones and other tool shapes,which can be mounted onto a machining apparatus, such as a grinding orpolishing apparatus.

Bonded abrasive tools usually have at least two phases includingabrasive grains and bond material. Certain bonded abrasive articles canhave an additional phase in the form of porosity. Bonded abrasive toolscan be manufactured in a variety of ‘grades’ and ‘structures’ that havebeen defined according to practice in the art by the relative hardnessand density of the abrasive composite (grade) and by the volumepercentage of abrasive grain, bond, and porosity within the composite(structure).

Some bonded abrasive tools may be particularly useful in grinding andshaping certain types of workpieces, including for example, metals,ceramics and crystalline materials, used in the electronics and opticsindustries. In other instances, certain bonded abrasive tools may beused in shaping of superabrasive materials for use in industrialapplications. In the context of grinding and shaping certain workpieceswith metal-bonded abrasive articles, generally the process involves asignificant amount of time and labor directed to maintaining the bondedabrasive article. That is, generally, metal-bonded abrasive articlesrequire regular truing and dressing operations to maintain the grindingcapabilities of the abrasive article.

The industry continues to demand improved methods and articles capableof grinding.

SUMMARY

According to a first aspect, an abrasive article includes a body havingabrasive grains contained within a bond material comprising a metal ormetal alloy. The body comprises a ratio of V_(AG)/V_(BM) of at leastabout 1.3, wherein V_(AG) is the volume percent of abrasive grainswithin the total volume of the body and V_(BM) is the volume percent ofbond material within the total volume of the body.

According to another aspect, an abrasive article includes a body havingabrasive grains contained within a bond material comprising a metal ormetal alloy, wherein the body comprises a ratio of V_(P)/V_(BM) of atleast about 1.5, wherein V_(P) is the volume percent of particulatematerial including abrasive grains and fillers within the total volumeof the body and V_(BM) is the volume percent of bond material within thetotal volume of the body. The bond material has an average fracturetoughness (K_(1c)) of not greater about 4.0 MPa m^(0.5).

In yet another aspect, an abrasive article includes a body havingabrasive grains contained within a bond material comprising a metal ormetal alloy, wherein the body comprises an active bond compositioncomprising at least about 1 vol % of an active bond composition of thetotal volume of the bond material. The body further includes a porosityof at least about 5 vol %, and wherein the bond material comprises anaverage fracture toughness (K_(1c)) of not greater about 4.0 MPam^(0.5).

In still another aspect, an abrasive article includes a body havingabrasive grains contained within a bond material comprising a metal ormetal alloy, wherein the body comprises a ratio of V_(P)/V_(BM) of atleast about 1.5, wherein V_(P) is the volume percent of particulatematerial including abrasive grains and fillers within the total volumeof the body and V_(BM) is the volume percent of bond material within thetotal volume of the body. The body includes at least about 5 vol %porosity of the total volume of the body, wherein a majority of theporosity is interconnected porosity defining a network of interconnectedpores extending through the volume of the body.

According to another aspect, an abrasive article includes a body havingabrasive grains contained within a bond material comprising a metal ormetal alloy, wherein the body comprises a ratio of V_(AG)/V_(BM) of atleast about 1.3, wherein V_(AG) is the volume percent of abrasive grainswithin the total volume of the body and V_(BM) is the volume percent ofbond material within the total volume of the body. The body includes anactive bond composition comprising at least 10 vol % of an active bondcomposition of the total volume of the bond material.

In yet another aspect, a method of forming an abrasive article includesforming a mixture including abrasive grains and bond material, whereinthe bond material comprises a metal or metal alloy, and shaping themixture to form a green article. The method further includes sinteringthe green article at a temperature to conduct liquid phase sintering andform an abrasive body including the abrasive grains contained within thebond material, wherein the body comprises a ratio of V_(P):V_(BM) of atleast about 3:2, wherein V_(P) is the volume percent of particulatematerial including abrasive grains and fillers within the total volumeof the body and V_(BM) is the volume percent of bond material within thetotal volume of the body.

Another aspect includes an abrasive article having a bonded abrasivebody including abrasive grains contained within a bond material made ofa metal or metal alloy, wherein the bond material comprises a compositematerial including a bond phase and a precipitated phase, theprecipitated phase having a composition including at least one elementof an active bond composition and at least one element of the bondmaterial.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure may be better understood, and its numerousfeatures and advantages made apparent to those skilled in the art byreferencing the accompanying drawings.

FIG. 1 includes a plot of grinding power (HP/in) versus number ofgrinding cycles for a bonded abrasive body according to an embodiment.

FIG. 2 includes a plot of surface roughness (Ra) versus number ofgrinding cycles for a bonded abrasive body according to an embodiment.

FIG. 3 includes a plot of grinding power (HP/in) versus number ofgrinding cycles for bonded abrasive bodies according to an embodimentand a conventional sample.

FIG. 4 includes a bar graph of grinding power (Hp) versus two differentmaterial removal rates (i.e., 4.5 in³/min/in and 5.1 in³/min/in) for abonded abrasive body according to an embodiment and a conventionalsample.

FIG. 5 includes a bar graph of grinding ratio (G-ratio) at two differentmaterial removal rates for a bonded abrasive body according to anembodiment and a conventional sample.

FIG. 6 includes a plot of spindle power (Hp) versus grinding time (sec)for a bonded abrasive body according to an embodiment and a conventionalsample.

FIG. 7 includes a plot of spindle power (Hp) versus grinding time (sec)for a bonded abrasive body according to an embodiment and a conventionalsample.

FIGS. 8-11 include magnified images of the microstructure of a bondedabrasive body according to an embodiment.

FIG. 12 includes a magnified image of a bonded abrasive body accordingto an embodiment.

The use of the same reference symbols in different drawings indicatessimilar or identical items.

DETAILED DESCRIPTION

The following is generally directed to bonded abrasive articlesincorporating abrasive grains within a three-dimensional matrix ofmaterial. Bonded abrasive articles utilize a volume of abrasive grainssecured within a three-dimensional matrix of bond material. Moreover,the following includes description related to methods of forming suchbonded abrasive articles and applications for such bonded abrasivearticles.

In accordance with an embodiment, the process for forming an abrasivearticle can be initiated by forming a mixture containing abrasive grainsand bond material. The abrasive grains can include a hard material. Forexample, the abrasive grains can have a Mohs hardness of at least about7. In other abrasive bodies, the abrasive grains can have a Mohshardness of at least 8, or even at least 9.

In particular instances, the abrasive grains can be made of an inorganicmaterial. Suitable inorganic materials can include carbides, oxides,nitrides, borides, oxycarbides, oxyborides, oxynitrides, and acombination thereof. Particular, examples of abrasive grains includesilicon carbide, boron carbide, alumina, zirconia, alumina-zirconiacomposite particles, silicon nitride, SiAlON, and titanium boride. Incertain instances, the abrasive grains can include a superabrasivematerial, such as diamond, cubic boron nitride, and a combinationthereof. In particular instances, the abrasive grains can consistessentially of diamond. In other embodiments, the abrasive grains canconsist essentially of cubic boron nitride.

The abrasive grains can have an average grit size of not greater thanabout 1000 microns. In other embodiments, the abrasive grains can havean average grit size of not greater than about 750 microns, such as notgreater than about 500 microns, not greater than about 250 microns, notgreater than about 200 microns, or even not greater than about 150microns. In particular instances, the abrasive grains of embodimentsherein can have an average grit size, within a range between about 1micron and about 1000 microns, such as between about 1 micron and 500microns, or even between about 1 microns and 200 microns.

In further reference to the abrasive grains, the morphology of theabrasive grains can be described by an aspect ratio, which is a ratiobetween the dimensions of length to width. It will be appreciated thatthe length is the longest dimension of the abrasive grit and the widthis the second longest dimension of a given abrasive grit. In accordancewith embodiments herein, the abrasive grains can have an aspect ratio(length:width) of not greater than about 3:1 or even not greater thanabout 2:1. In particular instances, the abrasive grains can beessentially equiaxed, such that they have an aspect ratio ofapproximately 1:1.

The abrasive grains can include other features, including for example, acoating. The abrasive grains can be coated with a coating material whichmay be an inorganic material. Suitable inorganic materials can include aceramic, a glass, a metal, a metal alloy, and a combination thereof. Inparticular instances, the abrasive grains can be electroplated with ametal material and, more particularly, a transition metal composition.Such coated abrasive grains may facilitate improved bonding (e.g.,chemical bonding) between the abrasive grains and the bond material.

In certain instances, the mixture can include a particular distributionof abrasive grains. For example, the mixture can include a multi-modaldistribution of grit sizes of abrasive grains, such that a particulardistribution of fine, intermediate, and coarse grit sizes are presentwithin the mixture. In one particular instance the mixture can include abimodal distribution of abrasive grains including fine grains having afine average grit size and coarse abrasive grains having a coarseaverage grit size, wherein the coarse average grit size is significantlygreater than the fine average grit size. For instance, the coarseaverage grit size can be at least about 10% greater, at least about 20%,at least about 30%, or even at least about 50% greater than the fineaverage grit size (based on the fine abrasive grit size). It will beappreciated that the mixture can include other multi-modal distributionof abrasive grains, including for example, a tri-modal distribution or aquad-modal distribution.

It will also be appreciated that abrasive grains of the same compositioncan have various mechanical properties, including for example,friability. The mixture, and the final-formed bonded abrasive body, canincorporate a mixture of abrasive grains, which may be the samecomposition, but having varying mechanical properties or grades. Forexample, the mixture can include abrasive grains of a singlecomposition, such that the mixture includes only diamond or cubic boronnitride. However, the diamond or cubic boron nitride can include amixture of different grades of diamond or cubic boron nitride, such thatthe abrasive grains having varying grades and varying mechanicalproperties.

The abrasive grains can be provided in the mixture in an amount suchthat the finally-formed abrasive article contains a particular amount ofabrasive grains. For example, the mixture can include a majority content(e.g., greater than 50 vol %) of abrasive grains.

In accordance with an embodiment, the bond material can be a metal ormetal alloy material. For example, the bond material can include apowder composition including at least one transition metal element. Inparticular instances, the bond material can include a metal selectedfrom the group including copper, tin, silver, molybdenum, zinc,tungsten, iron, nickel, antimony, and a combination thereof. In oneparticular embodiment, the bond material can be a metal alloy includingcopper and tin. The metal alloy of copper and tin can be a bronzematerial, which may be formed of a 60:40 by weight composition of copperand tin, respectively.

According to a particular embodiment, the metal alloy of copper and tincan include a certain content of copper, such that the final-formedbonded abrasive article has suitable mechanical characteristics andgrinding performance. For example, the copper and tin metal alloy caninclude not greater than about 70% copper, such as not greater thanabout 65% copper, not greater than about 60% not greater than about 50%copper, not greater than about 45% copper, or even not greater thanabout 40% copper. In particular instances, the amount of copper iswithin a range between about 30% and about 65%, and more particularly,between about 40% and about 65%.

Certain metal alloys of copper and tin can have a minimum amount of tin.For example, the metal alloy can include at least about 30% tin of thetotal amount of the composition. In other instances, the amount of tincan be greater, such as at least about 35%, at least about 40%, at leastabout 45%, at least about 50%, at least about 60%, at least about 65%,or even at least about 75%. Certain bond materials can include a copperand tin metal alloy having an amount of tin within a range between about30% and about 80%, between about 30% and about 70%, or even betweenabout 35% and about 65%.

In an alternative embodiment, the bond material can be a tin-basedmaterial, wherein tin-based materials include metal and metal alloyscomprising a majority content of tin versus other compounds present inthe material. For example, the bond material can consist essentially oftin. Still, certain-tin-based bond materials may be used that includenot greater than about 10% of other alloying materials, particularlymetals.

The mixture can contain an equal portion of abrasive grains to bond.However, in certain embodiments, the mixture can be formed such that theamount of bond material can be less than the amount of abrasive grainswithin the mixture. Such a mixture facilitates a bonded abrasive articlehaving certain properties, which are described in more detail herein.

In addition to the abrasive grains and bond material, the mixture canfurther include an active bond composition precursor. The active bondcomposition precursor includes a material, which can be added to themixture that later facilitates a chemical reaction between certaincomponents of the bonded abrasive body, including for example,particulate material (e.g., abrasive grains and/or fillers) and bondmaterial. The active bond composition precursor can be added to themixture in minor amounts, and particularly, in amounts less than theamount of the abrasive grains present within the mixture.

In accordance with an embodiment, the active bond composition precursorcan include a composition including a metal or metal alloy. Moreparticularly, the active bond composition precursor can include acomposition or complex including hydrogen. For example, the active bondcomposition precursor can include a metal hydride, and moreparticularly, can include a material such as titanium hydride. In oneembodiment, the active bond composition precursor consists essentiallyof titanium hydride.

The mixture generally includes a minor amount of the active bondcomposition precursor. For example, the mixture can include not greaterthan about 40 wt % of the active bond composition precursor of the totalweight of the mixture. In other embodiments, the amount of the activebond composition precursor within the mixture can be less, such as notgreater than about 35 wt %, not greater than about 30 wt %, not greaterthan about 28 wt %, not greater than about 26 wt %, not greater thanabout 23 wt %, not greater than about 18 wt %, not greater than about 15wt %, not greater than about 12 wt %, or even not greater than about 10wt %. In particular instances, the amount of active bond compositionprecursor within the mixture can be within a range between about 2 wt %and about 40 wt %, such as between about 4 wt % and about 35 wt %,between about 8 wt % and about 28 wt %, between about 10 wt % and about28 wt %, or even between about 12 wt %, and about 26 wt %.

The mixture can further include a binder material. The binder materialmay be utilized to provide suitable strength during formation of thebonded abrasive article. Certain suitable binder materials can includean organic material. For example, the organic material can be a materialsuch as a thermoset, thermoplastic, adhesive and a combination thereof.In one particular instance, the organic material of the binder materialincludes a material such as polyimides, polyamides, resins, aramids,epoxies, polyesters, polyurethanes, acetates, celluloses, and acombination thereof. In one embodiment, the mixture can include a bindermaterial utilizing a combination of a thermoplastic material configuredto cure at a particular temperature. In another embodiment, the bindermaterial can include an adhesive material suitable for facilitatingattachment between components of the mixture. The binder can be in theform of a liquid, including for example, an aqueous-based ornon-aqueous-based compound.

Generally, the binder material can be present in a minor amount (byweight) within the mixture. For example, the binder can be present inamount significantly less than the amount of the abrasive grains, bondmaterial, or the active bond composition precursor. For example, themixture can include not greater than about 40 wt % of binder materialfor the total weight of the mixture. In other embodiments, the amount ofbinder material within the mixture can be less, such as not greater thanabout 35 wt %, not greater than about 30 wt %, not greater than about 28wt %, not greater than about 26 wt %, not greater than about 23 wt %,not greater than about 18 wt %, not greater than about 15 wt %, notgreater than about 12 wt %, or even not greater than about 10 wt %. Inparticular instances, the amount of binder material within the mixturecan be within a range between about 2 wt % and about 40 wt %, such asbetween about 4 wt % and about 35 wt %, between about 8 wt % and about28 wt %, between about 10 wt % and about 28 wt %, or even between about12 wt % and about 26 wt %.

The mixture can further include a certain amount of fillers. The fillerscan be a particulate material, which may be substituted for certaincomponents within the mixture, including for example, the abrasivegrains. Notably, the fillers can be a particulate material that may beincorporated in the mixture, wherein the fillers substantially maintaintheir original size and shape in the finally-formed bonded abrasivebody. Examples of suitable fillers can include oxides, carbides,borides, silicides, nitrides, oxynitrides, oxycarbides, silicates,graphite, silicon, inter-metallics, ceramics, hollow-ceramics, fusedsilica, glass, glass-ceramics, hollow glass spheres, natural materialssuch as shells, and a combination thereof.

Notably, certain fillers can have a hardness that is less than thehardness of the abrasive grains. Additionally, the mixture can be formedsuch that the fillers are present in an amount of not greater than about90 vol % of the total volume of the mixture. Volume percent is used todescribe the content of fillers as fillers can have varying densitydepending upon the type of particulate, such as hollow spheres versusheavy particulate. In other embodiments, the amount of filler within themixture can be not greater than about 80 vol %, such as not greater thanabout 70 vol %, not greater than about 60 vol %, not greater than about50 vol %, not greater than about 40 vol %, not greater than about 30 vol%, or even not greater than about 20 vol %.

Certain forming processes may utilize a greater amount of fillermaterial than the amount of abrasive grains. For example, nearly all ofthe abrasive grains can be substituted with one or more fillermaterials. In other instances, a majority content of the abrasive grainscan be substituted with filler material. In other embodiments, a minorportion of the abrasive grains can be substituted with filler material.

Moreover, the fillers can have an average particulate size that issignificantly less than the average grit size of the abrasive grains.For example, the average particulate size of the fillers can be at leastabout 5% less, such as at least about 10% less, such as at least about15% less, at least about 20% less, or even at least about 25% less thanthe average grit size of the abrasive grains based on the average gritsize of the average grit size of the abrasive grains.

In certain other embodiments, the fillers can have an averageparticulate size that is greater than the abrasive grains, particularlyin the context of fillers that are hollow bodies.

In particular instances, the filler material can have a fracturetoughness (KO of not greater than about 10 MPa m^(0.5), as measured by anano-indentation test via standardized test of ISO 14577 utilizing adiamond probe available from CSM Indentation Testers, Inc., Switzerlandor similar companies. In other embodiments, the filler can have afracture toughness (KO of not greater than about 9 MPa m^(0.5), such asnot greater than about 8 MPa m^(0.5), or even not greater than about 7MPa m^(0.5). Still, the average fracture toughness of the fillers can bewithin a range between about 0.5 MPa m^(0.5) about 10 MPa m^(0.5), suchas within a range between about 1 MPa m^(0.5) about 9 MPa m^(0.5), oreven within a range between about 1 MPa m^(0.5) about 7 MPa m^(0.5).

After forming the mixture, the process of forming the bonded abrasivearticle continues by shearing the mixture such that it has properrheological characteristics. For example, the mixture can be sheareduntil it has a particular viscosity, such as at least about 100Centipoise, and can have a consistency that is semi-liquid (e.g., amud-like consistency). In other instances, it could be of much lowerviscosity such as a paste.

After shearing the mixture, the process can continue by formingagglomerates from the mixture. Process of forming agglomerates caninitially include a process of drying the mixture. In particular thedrying process may be conducted at a temperature suitable to cure anorganic component (e.g., thermoset) within the binder contained withinthe mixture, and remove a portion of certain volatiles (e.g., moisture)within the mixture. Thus, upon suitable curing the organic materialwithin the binder material, the mixture can have a hardened orsemi-hardened form. Particularly suitable drying temperatures can be notgreater than about 250° C., and more particularly, within a rangebetween about 0° C. and about 250° C.

After drying the mixture at a suitable temperature, the process offorming agglomerates can continue by crushing the hardened form. Aftercrushing the hardened form, the crushed particles include agglomeratesof the components contained within the mixture, including the abrasivegrains and bond material. The process of forming the agglomerates canthen include sieving of the crushed particulate to obtain a suitabledistribution of agglomerate sizes.

After forming the agglomerates, the process can continue by shaping theagglomerates into a desirable shape of the finally-formed bondedabrasive article. One suitable shaping process includes filling a moldwith the agglomerated particles. After filling the mold, theagglomerates can be pressed to form a green (i.e., unsintered) bodyhaving the dimensions of the mold. In accordance with one embodiment,pressing can be conducted at a pressure of at least about 0.01 ton/in²of the area of the bonded abrasive article. In other embodiments, thepressure can be greater, such as on the order of at least about 0.1tons/in², at least about 0.5 tons/in², at least about 1 ton/in², or evenat least about 2 tons/in². In one particular embodiment pressing iscompleted at a pressure within a range between about 0.01 ton/in² andabout 5 tons/in², or more particularly, within a range between about 0.5tons/in² and about 3 tons/in².

After shaping the mixture to form the green article, the process cancontinue by treating the green article. Treating can include heattreating the green article, and particularly sintering of the greenarticle. In one particular embodiment, treating includes liquid phasesintering to form the bonded abrasive body. Notably, liquid phasesintering includes forming a liquid phase of certain components of thegreen article, particularly, the bond material, such that at thesintering temperature at least a portion of the bond material is presentin liquid phase and free-flowing. Notably, liquid phase sintering is nota process generally used for formation of bonded abrasives utilizing ametal bond material.

In accordance with an embodiment, treating the green article includesheating the green article to a liquid phase sintering temperature of atleast 400° C. In other embodiments, the liquid phase sinteringtemperature can be greater, such as at least 500° C., at least about650° C., at least about 800° C., or even at least about 900° C. Inparticular instances, the liquid phase sintering temperature can bewithin a range between about 400° C. and about 1100° C., such as betweenabout 800° C., and about 1100° C., and more particularly, within a rangebetween about 800° C. and 1050° C.

Treating, and particularly sintering, can be conducted for a particularduration. Sintering at the liquid phase sintering temperature can beconducted for a duration of at least about 10 minutes, at least about 20minutes, at least about 30 minutes, or even at least about 40 minutes.In particular embodiments, the sintering at the liquid phase sinteringtemperature can last for a duration within a range between about 10minutes and about 90 minutes, such as between about 10 minutes and 60minutes, or even between about 15 minutes and about 45 minutes.

Treating the green article can further include conducting a liquid phasesintering process in a particular atmosphere. For example, theatmosphere can be a reduced pressure atmosphere having a pressure of notgreater than about 10⁻² Torr. In other embodiments, the reduce pressureatmosphere can have a pressure of not greater than about 10⁻³ Torr, notgreater than about 10⁻⁴ Torr, such as not greater than about 10⁻⁵ Torr,or even not greater than about 10⁻⁶ Torr. In particular instances, thereduced pressure atmosphere can be within a range between about 10⁻²Torr and about 10⁻⁶ Torr.

Additionally, during treating the green article, and particularly duringa liquid phase sintering process, the atmosphere can be a non-oxidizing(i.e., reducing) atmosphere. Suitable gaseous species for forming thereducing atmosphere can include hydrogen, nitrogen, noble gases, carbonmonoxide, dissociated ammonia, and a combination thereof. In otherembodiments, an inert atmosphere may be used during treating of thegreen article, to limit oxidation of the metal and metal alloycomponents.

After completing the treating process, a bonded abrasive articleincorporating abrasive grains within a metal bond material is formed. Inaccordance with an embodiment, the abrasive article can have a bodyhaving particular features. For example, in accordance with oneembodiment, the bonded abrasive body can have a significantly greatervolume of abrasive grains than the volume of bond material within thebody. The bonded abrasive body can have a ratio of V_(AG)/V_(BM) of atleast about 1.3, wherein V_(AG) represents a volume percent of abrasivegrains within the total volume of the bonded abrasive body, and V_(BM)represents the volume percent of bond material within the total volumeof the bonded abrasive body. In accordance with another embodiment, theratio of V_(AG)/V_(BM) can be at least about 1.5, such as at least about1.7, at least about 2.0, at least about 2.1, at least about 2.2, or evenat least about 2.5. In other embodiments, the bonded abrasive body canbe formed such that the ratio of V_(AG)/V_(BM) is within a range betweenabout 1.3 and about 9.0, such as between about 1.3 and about 8.0, suchas between about 1.5 and about 7.0, such as between about 1.5 and about6.0, between about 2.0 and about 5.0, between about 2.0 and about 4.0,between about 2.1 and about 3.8, or even between about 2.2 and about3.5.

In more particular terms, the bonded abrasive body can include at leastabout 30 vol % abrasive grains for the total volume of the bondedabrasive body. In other instances, the content of abrasive grains isgreater, such as at least about 45 vol %, at least about 50 vol %, atleast about 60 vol %, at least about 70 vol %, or even at least about 75vol %. In particular embodiments, the bonded abrasive body comprisesbetween about 30 vol % and about 90 vol %, such as between about 45 vol% and about 90 vol %, between about 50 vol % and about 85 vol %, or evenbetween about 60 vol % and about 80 vol % abrasive grains for the totalvolume of the bonded abrasive body.

The bonded abrasive body can include not greater than about 45 vol %bond material for the total volume of the bonded abrasive body.According to certain embodiments, the content of bond material is less,such not greater than about 40 vol %, not greater than about 30 vol %,not greater than about 25 vol %, not greater than about 20 vol %, oreven not greater than about 15 vol %. In particular embodiments, thebonded abrasive body comprises between about 5 vol % and about 45 vol %,such as between about 5 vol % and about 40 vol %, between about 5 vol %and about 30 vol %, or even between about 10 vol % and about 30 vol %bond material for the total volume of the bonded abrasive body.

In accordance with another embodiment, the bonded abrasive body hereincan include a certain amount of porosity. For example, the bondedabrasive body can have at least 5 vol % porosity for the total volume ofthe bonded abrasive body. In other embodiments, the bonded abrasive bodycan have at least about 10 vol %, such as at least about 12 vol %, atleast about 18 vol %, at least about 20 vol %, at least about 25 vol %,at least about 30 vol %, or even at least about 35 vol % porosity forthe total volume of the body. Still, in other embodiments, the bondedabrasive body can include not greater than about 80 vol % porosity forthe total volume of the body. In other articles, the bonded abrasivebody can have not greater than about 70 vol %, not greater than about 60vol %, 55 vol % porosity, such as not greater than about 50 vol %porosity, not greater than about 48 vol % porosity, not greater thanabout 44 vol % porosity, not greater than about 40 vol % porosity, oreven not greater than about 35 vol % porosity for the total volume ofthe body. It will be appreciated that the porosity can fall within arange between any of the minimum and maximum values listed herein.

The bonded abrasive body can be formed such that a certain content ofthe porosity within the bonded abrasive body is interconnected porosity.Interconnected porosity defines a network of interconnected channels(i.e., pores) extending through the volume of the bonded abrasive body.For example, a majority of the porosity of the body can beinterconnected porosity. In fact, in particular instances, the bondedabrasive body can be formed such that at least 60%, at least about 70%,at least about 80%, at least about 90%, or even at least about 95% ofthe porosity present within the bonded abrasive body is interconnectedporosity. In certain instances, essentially all of the porosity presentwithin the body is interconnected porosity. Accordingly, the bondedabrasive body can be defined by a continuous network of two phases, asolid phase defined by the bond and abrasive grains and a secondcontinuous phase defined by the porosity extending between the solidphase throughout the bonded abrasive body.

In accordance with another embodiment, the bonded abrasive body can havea particular ratio of particulate material (V_(P)), which includesabrasive grains and fillers, as compared to the bond material (V_(BM))for the total volume of the bonded abrasive body. It will be appreciatedthat the amounts of the particulate material and the bond material aremeasured in volume percent of the component as part of the total volumeof the body. For example, the bonded abrasive body of embodiments hereincan have a ratio (V_(P)/V_(BM)) of at least about 1.5. In otherembodiments, the ratio (V_(P)/V_(BM)) can be at least about 1.7, atleast about 2.0, at least about 2.2, at least about 2.5, or even atleast about 2.8. In particular instances, the ratio (V_(P)/V_(BM)) canbe within a range between 1.5 and about 9.0, such as between about 1.5and 8.0, such as between about 1.5 and about 7.0, between about 1.7 andabout 7.0, between about 1.7 and about 6.0, between about 1.7 and about5.5, or even between about 2.0 and about 5.5. As such, the bondedabrasive body can incorporate a higher content of particulate materialincluding fillers and abrasive grains than bond material.

According to one embodiment, the abrasive body can include an amount(vol %) of fillers that can be less than, equal to, or even greater thanthe amount (vol %) of abrasive grains present within the total volume ofthe bonded abrasive body. Certain abrasive articles can utilize notgreater than about 75 vol % fillers for the total volume of the bondedabrasive body. According to certain embodiments, the content of fillersin the body can be not greater than about 50 vol %, not greater thanabout 40 vol %, not greater than about 30 vol %, not greater than about20 vol %, or even not greater than about 15 vol %. In particularembodiments, the bonded abrasive body comprises between about 1 vol %and about 75 vol %, such as between about 1 vol % and about 50 vol %,between about 1 vol % and about 20 vol %, or even between about 1 vol %and about 15 vol % fillers for the total volume of the bonded abrasivebody. In one instance, the bonded abrasive body can be essentially freeof fillers.

The bonded abrasive bodies of embodiments herein can have a particularcontent of active bond composition. As will be appreciated the activebond composition can be a reaction product formed from a reactionbetween the active bond composition precursor and certain components ofthe bonded abrasive body, including for example, abrasive grains,fillers, and bond material. The active bond composition can facilitatechemical bonding between the particulates (e.g., abrasive grains orfiller) within the body and the bond material, which may facilitateretention of particulates within the bond material.

In particular, the active bond composition can include distinct phases,which can be disposed in distinct regions of the bonded abrasive body.Moreover, the active bond composition can have a particular compositiondepending upon the location of the composition. For example, the activebond composition can include a precipitated phase and an interfacialphase. The precipitated phase can be present within the bond materialand can be dispersed as a distinct phase throughout the volume of thebond material. The interfacial phase can be disposed at the interfacebetween the particulate material (i.e., abrasive grains and/or fillers)and the bond material. The interfacial phase can extend around amajority of the surface area of the particulate material of the body.While not completely understood, it is theorized that the distinctphases and differences in the composition of the active bond compositionare due to the forming processes, particularly liquid phase sintering.

Accordingly, the bond material can be a composite material including abond phase and a precipitated phase, which are separate phases. Theprecipitated phase can be made of a composition including at least oneelement of the active bond composition and at least one element of thebond material. Notably, the precipitated phase can include at least onemetal element originally provided in the mixture as the bond material.The precipitated phase can be a metal or metal alloy compound orcomplex. In particular embodiments, the precipitated phase can include amaterial selected from the group of materials consisting of titanium,vanadium, chromium, zirconium, hafnium, tungsten, and a combinationthereof. In more particular instances, the precipitated phase includestitanium, and may consist essentially of titanium and tin.

The bond phase of the bond material can include a transition metalelement, and particularly a metal element included in the original bondmaterial used to form the mixture. As such, the bond phase can be formedof a material selected from the group of metals consisting of copper,tin, silver, molybdenum, zinc, tungsten, iron, nickel, antimony, and acombination thereof. In particular instances, the bond phase can includecopper, and may be a copper-based compound or complex. In certainembodiments, the bond phase consists essentially of copper.

The interfacial phase can include at least one element of the activebond composition. Moreover, the interfacial phase can include at leastone element of the particulate material. As such, the interfacial phasecan be a compound or complex formed through a chemical reaction betweenthe active bond composition and the particulate. Certain interfacialphase materials include carbides, oxides, nitrides, borides,oxynitrides, oxyborides, oxycarbides and a combination thereof. Theinterfacial phase can include a metal, and more particularly, may be acompound incorporating a metal, such as a metal carbide, metal nitride,metal oxide, metal oxynitride, metal oxyboride, or metal oxycarbide.According to one embodiment, the interfacial phase consists essentiallyof a material from the group of titanium carbide, titanium nitride,titanium boronitride, titanium aluminum oxide, and a combinationthereof.

Moreover, the interfacial phase can have an average thickness of atleast about 0.1 microns. However, and more particularly, the interfacialphase can have a varying thickness depending upon the size of theparticulate material the interfacial phase overlies. For example, withregard to abrasive grains and/or fillers having an average size of lessthan 10 microns, the interfacial phase can have a thickness within arange between about 1% to 205 of the average size of the particulate.For particulate material having an average size within a range betweenabout 10 microns and about 50 microns, the interfacial phase can have athickness within a range between about 1% to about 10% of the averagesize of the particulate. For particulate material having an average sizewithin a range between about 50 microns and about 500 microns, theinterfacial phase can have a thickness within a range between about 0.5%to about 10% of the average size of the particulate. For particulatematerial having an average size of greater than about 500 microns, theinterfacial phase can have a thickness within a range between about 0.1%to about 0.5% of the average size of the particulate.

FIGS. 8-11 include magnified images of the microstructure of a bondedabrasive body in accordance with an embodiment. FIG. 8 includes ascanning electron microscope image (operated in backscatter mode) of across-section of a portion of a bonded abrasive body including abrasivegrains 801 and bond material 803 extending between the abrasive grains801. As illustrated, the bond material 803 includes two distinct phasesof material, a precipitated phase 805 represented by a lighter color andextending through the volume of the bond material 803, and a bond phase806 represented by a darker color and extending through the volume ofthe bond material 803.

FIGS. 9-11 include magnified images of the same area of the bondedabrasive body of FIG. 8, using microprobe analysis to identify selectelements present in certain regions of the body. FIG. 9 includes amicroprobe image of the region of FIG. 8 in a mode set to identifyregions high in copper, such that the lighter regions indicate regionswhere copper is present. According to an embodiment, the bond material803 can include a metal alloy of copper and tin. According to a moreparticular embodiment, the bond phase 806 of the bond material 803,which is one of at least two distinct phases of the bond material 803,can have a greater amount of copper present than the precipitated phase805.

FIG. 10 includes a magnified image of the region of FIGS. 8 and 9, usingmicroprobe analysis to identify select elements present in certainregions of the bonded abrasive body. FIG. 10 uses a microprobe in a modeset to identify regions having tin present, such that the lighterregions indicate regions where tin is more prevalent. As illustrated,the precipitated phase 805 of the bond material 803 has a greatercontent of tin than the bond phase 806.

FIG. 11 includes a magnified image of the region of FIG. 8-10, usingmicroprobe analysis. In particular, FIG. 11 uses a microprobe in a modeset to identify regions having titanium present, such that the lighterregions indicate regions where titanium is more prevalent. Asillustrated, the precipitated phase 805 of the bond material 803 has agreater content of titanium than the bond phase 806. FIG. 11 alsoprovides evidence of the interfacial phase 1101 at the interface of theabrasive grains 801 and the bond material 803. As evidenced by FIG. 11,the interfacial phase 1101 includes a particularly high content oftitanium, indicating that the titanium of the active bond compositionprecursor may preferentially migrate to the interface of the particulate(i.e., abrasive grains 801) and chemically react with the abrasivegrains to form an interracial phase compound as described herein.

FIGS. 8-11 provide evidence of an unexpected phenomenon. While it is notcompletely understood, the original bond material comprising copper andtin is separated during processing, which is theorized to be due to theliquid phase sintering process. The tin and copper become distinctphases; the precipitated phase 805 and the bond phase 806, respectively.Moreover, the tin preferentially combines with the titanium, present inthe active bond composition precursor material to form the precipitatedphase 805.

In accordance with an embodiment, the bonded abrasive body can includeat least about 1 vol % of the active bond composition, which includesall phases of the active bond composition, such as the interfacial phaseand the precipitate phase, for the total volume of the bond material. Inother instances, the amount of active bond composition within the bondcan be greater, such at least about 4 vol %, at least about 6 vol %, atleast about 10 vol %, at least about 12 vol %, at least about 14 vol %,at least about 15 vol %, or even at least about 18 vol %. In particularinstances, the bond material contains an amount of active bondcomposition within the range between about 1 vol % and about 40 vol %,such as between about 1 vol % and 30 vol %, between about 1 vol % andabout 25 vol %, between about 4 vol % and about 25 vol %, or betweenabout 6 vol % and about 25 vol %. In some instances, the amount ofactive bond composition is within a range between about 10 vol % andabout 30 vol %, between about 10 vol % and about 25 vol %, or evenbetween about 12 vol % and about 20 vol % of the total volume of thebond material.

The bonded abrasive body can be formed such that the bond material canhave a particular fracture toughness (K_(1c)). The toughness of the bondmaterial may be measured via a micro-indentation test ornano-indentation test. Micro-indentation testing measures the fracturetoughness through a principle of generating cracks on a polished samplethrough loading an indentor at a particular location within thematerial, including for example in the present instance, in the bondmaterial. For example, a suitable micro-indentation test can beconducted according to the methods disclosed in “Indentation of Brittlematerials”, Microindentation Techniques in Materials Science andEngineering, ASTM STP 889, D. B. Marshall and B. R. Lawn pp 26-46. Inaccordance with an embodiment, the bonded abrasive body has a bondmaterial having an average fracture toughness (K_(1c)) of not greaterthan about 4.0 MPa m^(0.5). In other embodiments, the average fracturetoughness (K_(1c)) of the bond material can be not greater about 3.75MPa m^(0.5), such as not greater about 3.5 MPa m^(0.5), not greaterabout 3.25 MPa m^(0.5), not greater about 3.0 MPa m^(0.5), not greaterabout 2.8 MPa m^(0.5), or even not greater about 2.5 MPa m^(0.5). Theaverage fracture toughness of the bond material can be within a rangebetween about 0.6 MPa m^(0.5) about 4.0 MPa m^(0.5), such as within arange between about 0.6 MPa m^(0.5) about 3.5 MPa m^(0.5), or evenwithin a range between about 0.6 MPa m^(0.5) about 3.0 MPa m^(0.5).

The abrasive articles of the embodiments herein may have particularproperties. For example, the bonded abrasive body can have a modulus ofrupture (MOR) of at least about 2000 psi, such as at least about 4000psi, and more particularly, at least about 6000 psi.

The bonded abrasive bodies of the embodiments herein demonstrateparticular properties when used in certain grinding operations. Inparticular, the bonded abrasive wheels can be used in non-dressedgrinding operations, wherein the bonded abrasive body does not require adressing operation after the body has undergone a truing operation.Traditionally, truing operations are completed to give the abrasive bodya desired contour and shape. After truing, the abrasive body is dressed,typically with an equally hard or harder abrasive element to remove worngrit and expose new abrasive grains Dressing is a time consuming andnecessary process for conventional abrasive articles to ensure properoperation of the abrasive article. The bonded abrasive bodies of theembodiments herein have been found to require significantly lessdressing during use and have performance parameters that aresignificantly improved over conventional abrasive articles.

For example, in one embodiment, during a non-dressed grinding operation,the bonded abrasive body of an embodiment, can have a power variance ofnot greater than about 40%, wherein power variance is described by theequation [(Po−Pn)/Po]×100%. Po represents the grinding power (Hp orHp/in) to grind a workpiece with the bonded abrasive body at an initialgrinding cycle and Pn represents the grinding power (Hp or Hp/in) togrind the workpiece for a n^(th) grinding cycle, wherein n≧4.Accordingly, the power variance measures the change in grinding powerfrom an initial grinding cycle to a subsequent grinding cycle, whereinat least 4 grinding cycles are undertaken.

In particular, the grinding cycles can be completed in a consecutivemanner, which means no truing or dressing operations are conducted onthe bonded abrasive article between the grinding cycles. The bondedabrasive bodies of the embodiments herein can have a power variance ofnot greater than about 25% during certain grinding operations. In stillother embodiments, the power variance of the bonded abrasive body can benot greater than about 20%, such as not greater than about 15%, or evennot greater than about 12%. The power variance of certain abrasivebodies can be within a range between about 1% and about 40%, such asbetween about 1% and about 20%, or even between about 1% and about 12%.

In further reference to the power variance, it will be noted that thechange in grinding power between the initial grinding cycle (Po) and thegrinding power used to grind the workpiece at an nth grinding cycle (Pn)can be measured over a number of grinding cycles wherein “n” is greaterthan or equal to 4. In other instances, “n” can be greater than or equalto 6 (i.e., at least 6 grinding cycles), greater than or equal to 10, oreven greater than or equal to 12. Moreover, it will be appreciated thatthe nth grinding cycle can represent consecutive grinding cycles,wherein dressing is not completed on the abrasive article between thegrinding cycles.

In accordance with an embodiment, the bonded abrasive body can be usedin grinding operations, wherein the material removal rate (MRR′) is atleast about 1.0 in³/min/in [10 mm³/sec/mm]. In other embodiments, agrinding operation using a bonded abrasive body of embodiments herein,can be conducted at a material removal rate of at least about 4.0in³/min/in [40 mm³/sec/mm], such as at least about 6.0 in³/min/in [60mm³/sec/mm], at least about 7.0 in³/min/in [70 mm³/sec/mm], or even atleast about 8.0 in³/min/in [80 mm³/sec/mm]. Certain grinding operationsutilizing the bonded abrasive bodies of embodiments herein can beconducted at a material removal rate (MRR′) within a range between about1.0 in³/min/in [10 mm³/sec/mm] and about 20 in³/min/in [200 mm³/sec/mm],within a range between about 5.0 in³/min/in [50 mm³/sec/mm] and about 18in³/min/in [180 mm³/sec/mm], within a range between about 6.0 in³/min/in[60 mm³/sec/mm] and about 16 in³/min/in [160 mm³/sec/mm] or even withina range between about 7.0 in³/min/in [70 mm³/sec/mm] and about 14in³/min/in [140 mm³/sec/mm].

Moreover, the bonded abrasive body can be utilized in grindingoperations wherein the bonded abrasive body is rotated at particularsurface speeds. Surface speed refers to the speed of the wheel at thepoint of contact with the work piece. For example, the bonded abrasivebody can be rotated at a speed of at least 1500 surface feet per minute(sfpm), such as at least about 1800, such as at least about 2000 sfpm,at least about 2500 sfpm, at least about 5000 sfpm, or even at least10000 sfpm. In particular instances, the bonded abrasive body can berotated at a speed within a range between about 2000 sfpm and about15000 sfpm, such as between about 2000 sfpm and 12000 sfpm.

The bonded abrasive body may be suitable for use in various grindingoperations including for example plunge grinding operations, creep feedgrinding operations, peel grinding operations, flute grindingoperations, and the like. In one particular instance, the bondedabrasive body is suitable for use in end mill grinding applications. Inother instances, the bonded abrasive body may be useful in thinning ofhard and brittle workpieces, including for example, sapphire and quartzmaterials.

Furthermore, the bonded abrasive bodies of embodiments herein may beutilized in grinding operations, wherein after grinding, the workpiecehas an average surface roughness (Ra) that is not greater than about 50microinches (about 1.25 microns). In other instances, the averagesurface roughness of the workpiece can be not greater than about 40microinches (about 1 micron), or even not greater than about 30microinches (about 0.75 microns).

In other embodiments, during grinding with bonded abrasive articles ofembodiments herein, the average surface roughness variance for at leastthree consecutive grinding operations can be not greater than about 35%.It should be noted that consecutive grinding operations are operationswherein a truing operation is not conducted between each of the grindingoperations. The variance in the average surface roughness can becalculated as a standard deviation of the measured average surfaceroughness (Ra) of the workpiece at each of the locations on theworkpiece, where each separate grinding operation is conducted. Inaccordance with certain embodiments, the average surface roughnessvariance for at least three consecutive grinding operations can be notgreater than about 25%, not greater than about 20%, not greater thanabout 15%, not greater than about 10%, or even not greater than about5%.

In accordance with other embodiments, the bonded abrasive article canhave a G-ratio of at least about 1200. The G-ratio is the volume ofmaterial removed from the workpiece divided by the volume of materiallost from the bonded abrasive body through wear. In accordance withanother embodiment, the bonded abrasive body can have a G-ratio of atleast about 1300, such as at least about 1400, at least about 1500, atleast about 1600, at least about 1700, or even at least about 1800. Incertain instances, the G-ratio of the bonded abrasive body can be withina range between about 1200 and about 2500, such as between about 1200and about 2300, or even between about 1400 and about 2300. The G-ratiovalues noted herein can be achieved at the material removal rates notedherein. Moreover, the G-ratio values described can be achieved on avariety of workpiece material types described herein.

In other terms, the bonded abrasive article can have a G-ratio that issignificantly improved over conventional abrasive articles, particularlymetal-bonded abrasive articles. For instance, the G-ratio of the bondedabrasive bodies according to embodiments herein can be at least about 5%greater than the G-ratio of a conventional abrasive article. In otherinstances, the improvement in G-ratio can be greater, such as at leastabout 10%, at least about 15%, at least about 20%, at least about 25%,or even at least about 30%. Particular embodiments of the bondedabrasive article demonstrate an increase in G-ratio as compared to aconventional bonded abrasive within a range between about 5% and about200%, between about 5% and about 150%, between about 5% and about 125%,between about 5% and about 100%, between about 10% and about 75% or evenbetween about 10% and about 60%.

Certain bonded abrasive bodies demonstrate an initial grinding powerthat is sufficiently close to a steady state grinding power. Generally,the steady state grinding power is significantly different from aninitial grinding power for conventional metal-bonded abrasive articles.As such, the increase in the grinding power from an initial grindingpower is particularly low for the bonded abrasive bodies of embodimentsherein as compared to conventional metal-bonded abrasive articles. Forexample, the bonded abrasive bodies of the embodiments herein can havean increase in the initial grinding power of not greater than about 40%as defined by the equation [(Pn−Po)/Po]×100%. In the equation, Porepresents the initial grinding power (Hp or Hp/in) to grind theworkpiece with the bonded abrasive body at an initial grinding cycle andPn represents the grinding power (Hp or Hp/in) to grind the workpiecewith the bonded abrasive body at a n^(th) grinding cycle, wherein n≧16.It will be appreciated that the grinding cycles can be consecutivegrinding cycles, wherein no truing or dressing of the bonded abrasivebody is conducted.

According to one embodiment, during a grinding operation using thebonded abrasive article of embodiments herein, the increase in theinitial grinding power is not greater than about 35%, such as notgreater than about 30%, not greater than about 25%, not greater thanabout 20%, not greater than about 18%, not greater than about 15%, notgreater than about 12%, not greater than about 10%, or even not greaterthan about 8%. In particular instances, the bonded abrasive body iscapable of conducting grinding operations wherein the increase in theinitial grinding power can be within a range between about 0.1% andabout 40%, such as within a range between about 0.1% and about 30%,within a range between about 1% and about 15%, within a range betweenabout 1% and about 12%, or even within a range between about 1% andabout 8%.

In other embodiments, the bonded abrasive bodies demonstrate an increasein the initial grinding power of not greater than about 10% for agrinding time of at least 400 seconds at a minimum feed rate of about 3inches/min. The increase in initial grinding power can be defined by theequation [(P₄₀₀−Po)/Po]×100%, wherein Po represents the initial grindingpower (Hp or Hp/in) to initially grind the workpiece with the bondedabrasive body at a first grinding cycle and P₄₀₀ represents the grindingpower (Hp or Hp/in) to grind the workpiece with the bonded abrasive bodyafter 400 seconds of grinding. In certain other grinding operations, thebonded abrasive body can have an increase in the initial grinding powerof not greater than about 8%, such as not greater than about 6%, such asnot greater than about 4%, or even not greater than about 2% for agrinding time of at least 400 seconds at a minimum feed rate of about 3inches/min. In particular grinding applications, the bonded abrasivebody demonstrates an increase in the initial grinding power within arange between about 0.1% and about 10%, such as between about 0.1% andabout 8%, such as between about 0.1% and about 6%, or even between about0.1% and about 4%, for a grinding time of at least 400 seconds at aminimum feed rate of about 3 inches/min.

The bonded abrasive bodies of embodiments herein can have a particulargrinding performance, wherein the increase in initial grinding power isnot greater than about 20% for a grinding time of at least about 800seconds at a minimum feed rate of at least 3 inches/min. The increase ininitial grinding power for such applications can be defined by theequation [(P₈₀₀−Po)/Po]×100%, wherein Po represents the initial grindingpower (Hp or Hp/in) to initially grind the workpiece with the bondedabrasive body at a first grinding cycle and P₈₀₀ represents the grindingpower (Hp or Hp/in) to grind the workpiece with the bonded abrasive bodyafter 800 seconds of grinding. Still, for certain bonded abrasivearticles of embodiments herein, the increase in initial grinding powercan be less, such as not greater than about 15%, not greater than about10%, or even not greater than about 8% over a time of at least 800seconds at a minimum feed rate of 3 inches/min. The bonded abrasivebodies herein can have an increase in the initial grinding power withina range between about 0.1% and about 20%, such as between about 0.1% andabout 18%, such as between about 0.1% and about 15%, or even betweenabout 0.1% and about 8%, for a grinding time of at least 800 seconds ata minimum feed rate of about 3 inches/min. Such properties may beparticularly suitable for functioning of the bonded abrasive body whengrinding hard or superhard workpieces.

In accordance with another embodiment, the bonded abrasive body can havea limited increase in initial grinding power for a grinding time of atleast 800 seconds at a minimum feed rate of at least about 6 inches/min.For example, the increase in initial grinding power can be not greaterthan about 20%, such as not greater than about 15%, not greater thanabout 12%, or even not greater than about 10%, for a grinding time of atleast 800 seconds at a minimum feed rate of about 6 inches/min. Suchproperties may be particularly suitable for functioning of the bondedabrasive body when grinding hard or superhard workpieces.

The bonded abrasive bodies of the embodiments herein may be suitable forgrinding certain workpieces, such as particularly hard workpieces. Forexample, workpieces can have an average Vickers hardness of at least 5GPa. In other instances, the average Vickers hardness of the workpiecescan be at least about 10 GPa or even at least about 15 GPa.

The workpieces can be made of metals, metal alloys, nitrides, borides,carbides, oxides, oxynitrites, oxyborates, oxycarbides, in a combinationthereof. In particular instances, the workpieces can be metal carbides,including for example, tungsten carbide. In exemplary conditions wheregrinding is conducted on workpieces made of tungsten carbide, the amountof cobalt within the tungsten carbide workpiece can be within a rangebetween about 5% and about 12% by weight.

In conducting certain grinding operations, for example, on particularlyhard materials, the bonded abrasive body can be operated at a rate of atleast 1800 sfpm. In other instances, the bonded abrasive body can berotated at a rate of at least 1900 sfpm, at least about 2200 sfpm, oreven at least 2350 sfpm. In particular instances, the bonded abrasivebody can be rotated at a rate within a range between about 1800 sfpm andabout 3100 sfpm, more particularly, within a range between about 1900sfpm and about 2350 sfpm during grinding operations.

Additionally, the bonded abrasive articles of embodiments herein aresuitable for certain grinding operations, such as, for example, onparticularly hard workpieces at certain feed rates. For example, thefeed rate can be at least about 2 inches/min. In other instances, thefeed rate can be greater, such as at least about 3 inches/min, at leastabout 3.5 inches/min, or at least about 4 inches/min. Particularembodiments may utilize the bonded abrasive body in a grinding operationwherein the feed rate is within a range between about 2 inches/min andabout 10 inches/min, such as between about 3 inches/min and about 8inches/min.

In yet another embodiment, the bonded abrasive body can be used in agrinding operation wherein after truing the bonded abrasive body with anabrasive truing wheel, the bonded abrasive body is capable of grinding aworkpiece having an average Vickers hardness of at least 5 GPa for atleast 17 consecutive grinding cycles without exceeding the maximumspindle power of the grinding machine. As such, the bonded abrasivebodies demonstrate an improved working lifetime particularly in thecontext of grinding workpieces of hard material. In fact, the bondedabrasive body is capable of conducting at least about 20 consecutivegrinding cycles, at least about 25 consecutive grinding cycles, or atleast about 30 consecutive grinding cycles before a truing operation isutilized. It will be appreciated that reference to consecutive grindingcycles is reference to grinding cycles conducted in a continuous mannerwithout truing or dressing of the bonded abrasive body between grindingcycles.

In comparison of the bonded abrasive bodies of embodiments herein toconventional bonded abrasive bodies, generally, conventional bondedabrasive articles conduct not greater than about 16 consecutive grindingcycles on comparatively hard workpieces before requiring a truingoperation for resharpening and resurfacing. As such, the bonded abrasivebodies of embodiments herein demonstrate an improvement of operablegrinding time over conventional metal-bonded, bonded abrasives, asmeasured by the number of consecutive grinding cycles conducted before atruing operation is necessary or the grinding power exceeds the powercapabilities of the grinding machine.

Another noteworthy improvement in grinding performance as measured inthe industry is parts/dress, which is a measure of the number of partsthat can be machined by a particular abrasive article before theabrasive article requires dressing to maintain performance. According toone embodiment, the bonded abrasive bodies of the embodiments herein canhave an increase in grinding efficiency on a workpiece, as measured byparts/dress, of at least about 10% compared to a conventionalmetal-bonded abrasive article. According to another embodiment, theincrease in grinding efficiency is at least about 20%, such as at leastabout 30%, at least about 40%, or even at least about 50% as compared toconventional metal-bonded abrasive articles. Notably, such conventionalmetal-bonded abrasive articles can include state of the art articlessuch as G-Force and Spector brand abrasive articles available fromSaint-Gobain Corporation. In particular instances, the increase ingrinding efficiency as measured by parts/dress can be within a rangebetween about 10% and about 200%, such as on the order of between about20% and about 200%, between about 50% and about 200%, or even betweenabout 50% and about 150%. It will be appreciated, that such improvementscan be achieved on workpieces described herein under the grindingconditions described herein.

Additionally, the bonded abrasive articles of embodiments herein canhave an improvement in grinding performance as measured in the industryby wear rate, which is a measure of the wear an abrasive articleexperiences during grinding. According to one embodiment, the bondedabrasive bodies of the embodiments herein can have an improvement inwear rate, such that the abrasive article wears at a rate that is atleast 5% less than the wear rate of a conventional metal-bonded abrasivearticle. According to another embodiment, the wear rate is at leastabout 8% less, such as at least about 10%, at least about 12%, or evenat least about 15% as compared to conventional metal-bonded abrasivearticles. In particular instances, the improvement in wear rate can bewithin a range between about 5% and about 100%, such as on the order ofbetween about 5% and about 75%, between about 5% and about 0%, or evenbetween about 5% and about 50%. It will be appreciated, that suchimprovements can be achieved on workpieces described herein under thegrinding conditions described herein.

Another noteworthy improvement in grinding performance as measured inthe industry is wear rate, which is a measure of the wear an abrasivearticle experiences during grinding. According to one embodiment, thebonded abrasive bodies of the embodiments herein can have an improvementin wear rate, such that the abrasive article wears at a rate that is atleast 5% less than the wear rate of a conventional metal-bonded abrasivearticle. According to another embodiment, the wear rate is at leastabout 8% less, such as at least about 10%, at least about 12%, or evenat least about 15% as compared to conventional metal-bonded abrasivearticles. In particular instances, the improvement in wear rate can bewithin a range between about 5% and about 100%, such as on the order ofbetween about 5% and about 75%, between about 5% and about 60%, or evenbetween about 5% and about 50%. It will be appreciated, that suchimprovements can be achieved on workpieces described herein under thegrinding conditions described herein.

Another noted improvement in grinding performance demonstrated by theabrasive articles of the embodiments herein includes an increase inuseable grinding rate. Grinding rate is the speed at which a workpiececan be shaped without sacrificing the surface finish or exceeding thegrinding power of the machine or bonded abrasive article. According toone embodiment, the bonded abrasive bodies of the embodiments herein canhave an improvement in grinding rate, such that the abrasive article cangrind at a rate that is at least 5% faster than a conventionalmetal-bonded abrasive article. In other instances, the grinding rate canbe greater, such as at least about 8% less, at least about 10%, at leastabout 12%, at least about 15%, at least about 20%, or even at leastabout 25% as compared to conventional metal-bonded abrasive articles.For certain bonded abrasive articles herein, the improvement in grindingrate can be within a range between about 5% and about 100%, such as onthe order of between about 5% and about 75%, between about 5% and about60%, or even between about 5% and about 50%. It will be appreciated,that such improvements can be achieved on workpieces described hereinunder the grinding conditions described herein.

Notably, such improvements in the grinding rate can be achieved whilemaintaining other grinding parameters noted herein. For example,improvements in grinding rate can be achieved while also having limitedincrease in initial grinding power as noted herein, limited variance inthe surface finish as noted herein, and limited wear rate as notedherein.

FIG. 12 includes a magnified image of a bonded abrasive body accordingto an embodiment. As illustrated, the bonded abrasive body includesabrasive grains 1201 contained within and surrounded by a bond material1202 including a metal or metal alloy material. As further illustrated,the bonded abrasive body has a substantially open structure, includingpores 1203 extending between the abrasive grains 1201 and bond material1202. As evident from FIG. 12, the bonded abrasive body includes asignificant amount (vol %) of abrasive grains 1201, such that thestructure contains primarily abrasive grains 1201 which are bondedtogether by the bond material 1202. Moreover, the abrasive grains 1201are in close proximity to each other, and little bond material 1202separates the abrasive grains 1201, demonstrating the high ratio ofabrasive grains 1201 to bond material 1202.

EXAMPLES Example 1

A first bonded abrasive sample is made into a 4″ diameter wheel having a1A1 shape as understood in the industry. Forming of the sample includescreating a mixture including 45.96 grams of bronze powder (i.e., 60:40by weight of copper:tin) having a size of 325 U.S. mesh obtained fromConnecticut Engineering Associate Corporation located at 27 Philo CurtisRoad, Sandy Hook, Conn. 06482, USA. The bronze powder is dry blendedwith 5.11 grams of titanium hydride of same size purchased fromChemetall Chemical Products, New Providence N.J., USA. Abrasive grainsof cubic boron nitride having a US mesh size −120/+140 are also mixedwith the bronze powder and titanium hydride. The abrasive grains arefrom Saint-Gobain Ceramics and Plastics, Worcester, Mass. andcommercially available as CBN-V.

After adding the abrasive grains, 8.15 grams of organic binder is addedto the mixture and the mixture is sheared to a consistency of mud. Theorganic binder includes a thermoplastic resin sold under the brand nameS-binder by Wall Colmonoy Co. and a K424 binder from Vitta Corporation.The mixture is then oven dried to remove moisture. The dried mixture iscrushed and sieved to obtain agglomerates. The agglomerates are placedinto a steel mold having an annular shape and defining an outsidenominal diameter of 4 inches and an inside diameter of 3.2 inches. Theagglomerates are pressed at 2.4 tons/in² to form a green article. Thegreen article is sintered at 950° C. for 30 minutes in a reducingatmosphere having a pressure of approximately 10⁻⁴ Torr. Thefinally-formed bonded abrasive has a ratio (V_(AG)/V_(BM)) of 3.0 and anamount of porosity (100% interconnected porosity) of 34 volume percentof the total volume of the body.

A steel core is attached to the bonded abrasive body using epoxy andfurther finished, balanced and speed tested to complete the wheelmanufacturing process. The wheel was marked Sample 1 for identification.

Sample 1 is used to grind a workpiece of 52100 bearing steel, originallyhardened to 58-62 HRC, in an external cylindrical plunge grinding modeon a Bryant OD/ID grinder. The workpieces are in the form of 52100 steeldisks, 4 inches in diameter, and the grinding operation is an externalcylindrical plunge grind. Initially, before grinding, Sample 1 ismounted on the machine spindle and trued with a BPR diamond roll,commercially available from Saint-Gobain Abrasives, Arden, N.C., as BPRroll. The truing parameters are shown in Table 1.

TABLE 1 Wheel diameter, in 4 Wheel rpm 12675 Wheel speed, fpm 13273Dresser type BPR Dresser diameter, in 5.93 Dresser rpm 5482 Dressdirection Uni-directional (+) Speed or crush ratio +0.64 Depth of cutper pass, in 0.000080 Dresser width, in 0.012 Dresser traverse feed,in/sec 1.106 Dresser lead, in/rev 0.005 Overlap ratio 2

Sample 1 is not dressed with an abrasive stick after truing, as theabrasive grit are sufficiently exposed, reading the abrasive bodies fora non-dressed grinding operation. The grinding parameters are given inTable 2.

TABLE 2 Wheel diameter, in 4 Wheel rpm 13051 Wheel speed, fpm 13743 Workdiameter, in 3.7 Work rpm 168 Work speed, fpm 163 Wheel to work speedratio 84 Equivalent diameter, in 1.92 Wheel width, in 0.5 Work width, in0.25 Grind width, in 1.106 Mode of grinding Plunge Total infeed amount,in 0.015 Infeed rate, in/sec (Q′ = 0.5) 0.00071 Infeed rate, in/sec (Q′= 1.0) 0.00143 Infeed rate, in/sec (Q′ = 2.0) 0.00286

FIG. 1 includes a plot of grinding power (HP/in) versus number ofgrinding cycles for Sample 1 under the grinding conditions provided inTable 2 at two different material removal rates (MRR′) (i.e., 1in³/min/in and 2 in³/min/in). As demonstrated, plot 101 demonstratesthat Sample 1 is capable of grinding the workpiece at a MRR′ of 1in³/min/in at an initial grinding power of 11 Hp/in and a grinding powerafter 5 consecutive grinding cycles of 10 Hp/in. Plot 103 shows thatSample 1 is capable of grinding the workpiece at a MRR′ of 2 in³/min/inat an initial grinding power of 19 Hp/in and a grinding power after 5consecutive grinding cycles of 16 Hp/in. The power variance for Sample 1in grinding the workpiece at a MRR′ of 1 in³/min/in was 9% and the powervariance for Sample 1 in grinding the workpiece at a MRR′ of 2in³/min/in was 16%. Accordingly, Sample 1 demonstrates little variancebetween an initial grinding power and a steady state grinding powerafter 5 consecutive grinding operations. The workpiece had a width ofapproximately 0.25 inches and the abrasive wheel samples were formed tohave a width of 0.5 inches. The width used to calculate MRR′ was 0.25inches; the width of the workpiece.

FIG. 1 further includes two plots of grinding power (HP/in) versusnumber of grinding cycles for a conventional metal bonded abrasivearticle (Sample MBS1) commonly available as G-Force wheel B181-75UP061from Saint-Gobain Corporation. As demonstrated, plot 103 demonstratesthat Sample MBS1 is capable of grinding the workpiece at an initialgrinding power of 40 Hp/in at a MRR′ of 1 in³/min/in. After 5consecutive grinding cycles Sample MBS1 grinds at a power of 10 Hp/infor a MRR′ of 1 in³/min/in. Sample MBS1 demonstrates a power variance ina non-dressed grinding operation of 75%.

Plot 104 demonstrates that Sample MBS1 is capable of grinding theworkpiece at an initial grinding power of 50 Hp/in at a MRR′ of 2in³/min/in. After 5 consecutive grinding cycles Sample MBS1 grinds at apower of 10 Hp/in for a MRR′ of 2 in³/min/in. Sample MBS1 demonstrates apower variance in a non-dressed grinding operation of 84%. Clearly, in anon-dressed grinding operation the bonded abrasive articles of theembodiments herein demonstrate significantly improved performance ofgrinding power variance over the state-of-the-art abrasive wheels.

FIG. 2 includes a plot of surface finish or surface roughness (Ra)versus number of grinding cycles for Sample 1 under the grindingconditions provided in Table 2 at the two different material removalrates (MRR′) (i.e., 1 in³/min/in and 2 in³/min/in). As demonstrated,Sample, represented by plots 201 and 202, provides a surface finish (Ra)on the workpiece after consecutive grinding cycles of not greater thanabout 30 microinches at both material removal rates. Moreover, thevariance (i.e., the standard deviation of all measurements) of allmeasured surface finish values between the initial grinding operationand the fifth grinding cycle does not vary by more than 2.

FIG. 2 further includes surface finish (Ra) versus number of grindingcycles for Sample BMS 1 under the grinding conditions provided in Table2 at the two different material removal rates (MRR′) (i.e., 1 in³/min/inand 2 in³/min/in). As demonstrated by the plots 203 and 204,representing the surface finish achieved by Sample MBS1 at both materialremoval rates, was initially 30 microinches at both material removalrates, and rose significantly upon further consecutive grinding tovalues of 50 microinches and about 60 microinches at the materialremoval rates of 1 in³/min/in and 2 in³/min/in, respectively. Theaverage surface finish for Sample MBS1 at both material removal rateswas approximately 40 microinches and the variance in surface finish(standard deviation) was approximately 10 at both material removalrates. Clearly, Sample 1 is capable of providing superior surface finishon the workpiece after consecutive grinding cycles as compared to SampleMBS1.

Example 2

Sample 2 is created using the same process as Sample 1 provided herein.Sample 2 included an amount of fused silica filler material, which wassubstituted for 25% of the abrasive grain material. The fused silica wasof size −120/+140 U.S. mesh and procured from Washington Mills. Thefinally-formed bonded abrasive has a ratio (V_(P)/V_(BM)) of 2.3 and anamount of porosity (100% interconnected porosity) of 29% volume percentof the total volume of the body.

For comparison, a vitrified CBN wheel of specification B126-M160VT2B wasalso included in the test as Sample C1. Such a grinding wheel iscommonly available from Saint-Gobain Corporation as B126-M160VT2Babrasive wheel.

FIG. 3 includes a plot of grinding power (HP/in) versus number ofgrinding cycles for Sample 1, Sample 2, and Sample C1 the under thegrinding conditions provided in Table 2. A material removal rate of 2in³/min/in is used during grinding. As demonstrated by plot 301, Sample1 is capable of grinding the workpiece at an initial grinding power of18 Hp/in and a grinding power after 5 consecutive grinding cycles of 16Hp/in, for a power variance of approximately 16%. Plot 103 shows thatSample 2 was capable of grinding the workpiece at an initial grindingpower of 17 Hp/in and a grinding power after 5 consecutive grindingcycles of 15 Hp/in, for a power variance of approximately 12%. Bycomparison, the conventional, vitrified bonded abrasive sample had thesame change in power as Sample 2, and a power variance of approximately12%. As such, and quite unexpectedly, Samples 1 and 2, despite beingmetal-bonded abrasive articles, behave more like a vitrified bondedabrasive article with a brittle bond component and low power variance.

Example 3

A third sample (Sample 3) was made using the same forming processes asSample 1. The initial mixture is formed using 372 grams of a metal bondcomposition of 60/40 copper/tin, 41 grams of an active bond compositionprecursor of titanium hydride, 359 grams of abrasive grains of CBN-V ofsize B181, 131 grams of filler available as 38A alumina of size 100 meshfrom Saint-Gobain Grains and Powders, and 58 grams of the binder used inExample 1. Sample 3 has a ratio (V_(P)/V_(BM)) of 2.5 and porosity ofapproximately 29 vol %.

Sample 3 is used in a peel grinding operation on an outside diameter ofa workpiece made of 4140 steel in the shape of a round bar having adiameter of 5 inches and a length of 11 inches. The workpiece ishardened to 40-45 HRC. Sample 3 is compared to a conventional, vitrifiedCBN wheel commercially available from Saint Gobain Abrasives asB150-M150-VT2B (Sample C2).

Sample 3 is formed into a large bonded abrasive wheel, mounted on theperiphery of a steel disk to form a 20 inch diameter wheel. Sample 3 istrued using a diamond roll and used to grind the workpiece without anysubsequent dressings to expose the grit. Truing conditions are shown inTable 3 below. The grinding conditions are shown in Table 4.

TABLE 3 Truing of wheels for Peel grinding of 4140 steel Wheel speed,sfpm 26,000 Truing direction Cross-axial, diamond roll perpendicular towheel axis Truing wheel Diamond roll, BPR Roll speed, sfpm 10,200 Depthof cut per pass, in. 0.0002 Traverse rate, in/rev 0.015 Roll diameter,in 4.7

TABLE 4 Grinding parameters for Peel grinding of 4140 steel Wheel speed,sfpm 26,000 Work speed, sfpm 250 Radial depth of cut, in/pass 0.008 Rollspeed, sfpm 10,200 Feed rate, in/rev 0.04 Number of passes 10 MachineWeldon 1632 Gold grinder

The results are summarized in FIGS. 4 and 5. FIG. 4 includes a bar graphof grinding power (Hp) versus two different material removal rates(i.e., 9.6 in³/min/in and 12 in³/min/in). Bar 401 represents thegrinding power used during grinding of the workpiece by Sample 3 afteran initial pass at a material removal rate of 9.6 in³/min/in. Bar 402represents the grinding power of Sample 3 during grinding of theworkpiece after 25 consecutive grinding cycles (i.e., passes) on theworkpiece at the material removal rate of 9.6 in³/min/in. Asillustrated, Sample 3 demonstrates a very small change in the grindingpower over 25 consecutive grinding cycles without undergoing a truingoperation. In fact, the change in grinding power is estimated to be lessthan about 12%.

Bars 403 and 404 demonstrate the grinding power used during grinding ofSample C2 and after 25 consecutive grinding cycles (i.e., passes) on theworkpiece at the material removal rate of 9.6 in³/min/in. In acomparison of Sample 3 with Sample C2, it is noted that Sample 3 behavesmore like a vitrified bonded abrasive article than conventional metalbonded abrasive articles.

Bar 405 represents the grinding power used during grinding of theworkpiece by Sample 3 after an initial pass at a material removal rateof 12 in³/min/in. Bar 406 represents the grinding power of Sample 3during grinding of the workpiece after 25 consecutive grinding cycles(i.e., passes) on the workpiece at the material removal rate of 12in³/min/in. Again, Sample 3 demonstrates a very small change in thegrinding power over 25 consecutive grinding cycles without undergoing atruing operation. In fact, the change in grinding power is estimated tobe less than about 10%.

Bars 407 and 408 demonstrate the grinding power used during grinding ofthe workpiece by Sample C2 and at an initial pass and after 25consecutive grinding cycles (i.e., passes) on the workpiece at thematerial removal rate of 12 in³/min/in. In a comparison of Sample 3 withSample C2, it is noted that Sample 3 behaves more like a vitrifiedbonded abrasive article than conventional metal bonded abrasivearticles.

FIG. 5 includes a bar graph of grinding ratio (G-ratio) versus twodifferent material removal rates (i.e., 9.6 in³/min/in and 12in³/min/in) for Sample 3 and Sample C2. As illustrated, at both materialremoval rates, Sample 3 has a G-ratio that is significantly greater thanSample C2. In fact, while the spindle power and surface finish werevirtually the same for Sample 3 as compared to Sample C2, the G-ratio ofthe Sample 3 is 35% to 50% greater than the G-ratio of Sample C1 at bothmaterial removal rates.

Example 4

A fourth sample (Sample 4) is created according to the processesprovided in Example 1. The initial mixture is formed from 138 grams of ametal bond composition of 60/40 copper-tin, 15 grams of titanium hydrideas an active bond component precursor, 20 grams of the organic binder ofExample 1, and 164 grams of diamonds available from Saint-GobainCeramics and Plastics as RB 270/325 U.S. mesh, diamond grits. Sample 4has a ratio (V_(AG)/V_(BM)) of 2.3 and porosity of approximately 36 vol%.

The grinding operation includes fluting of a tungsten carbide workpieceof 1 inches in diameter and 10% by weight of cobalt as binder. Thegrinding performance of Sample 4 was tested against a state-of-the-artmetal bonded wheel (G-Force Abrasive available from Saint-GobainCorporation) having 18.75 vol % abrasive grains, 71.25 vol % bond,diamond abrasive grains of type RB 270/325 U.S. mesh.

Both samples were trued and dressed off-line before use. The sampleswere mounted on a steel arbor and balanced. The sample is trued with asilicon carbide wheel of 100 grit, H grade and vitrified bond, commonlyused for such processes. The sample is rotated at about 1/10 the surfacespeed of the silicon carbide wheel that is run at approximately 5000sfpm. While the sample wheel is rotating, it is trued at 0.001″ depth ofcut and 10 in/min. traverse rate until the wheel is considered true.Each sample is also dressed with a silicon carbide wheel of 200 mesh toexpose the grit for grinding. Dressing with the stick is completed atthe beginning of all grinds to start from same reference point.

The results of the grinding test are provided in FIG. 6. FIG. 6 includesa plot of spindle power (Hp) versus grinding time (sec) for Sample 1under three different conditions and Sample C2 in one condition. SampleC2 is represented by plot 601 and grinding was conducted at a wheelspeed of 3000 rpm and a grinding rate of 3.75 inches/min. Asillustrated, Sample C2 experienced a significant increase in grindingpower necessary for consecutive grinding cycles. The initial grindingpower is approximately 1.8 Hp and increases dramatically to 3 Hp over 16grinding cycles for a duration of approximately 1200 seconds. Sample C2experienced an increase in grinding power from the threshold grindingpower of at least 40%.

By contrast, Sample 4 demonstrated significantly less increase ininitial grinding power for various grinding conditions. Plot 602demonstrates the grinding power of Sample 4 on the workpiece at 3000 rpmand a grinding rate of 3.75 inches/min. The conditions are identical tothe grinding conditions used to test Sample C2. As illustrated by plot602, Sample 4 has a initial grinding power of approximately 1.5 Hp and afinal grinding power 2 Hp after 16 consecutive grinding cycles at nearly1200 seconds. Sample 4 demonstrates an increase in the threshold powerof only 25%. Sample 4 demonstrates a significantly improved operablegrinding lifetime as compared to Sample C2.

Plot 603 demonstrates the grinding power of Sample 4 on the workpiece at2500 rpm and a grinding rate of 3.75 inches/min. As illustrated by plot603, Sample 4 has a initial grinding power of approximately 1.8 Hp and afinal grinding power of 1.8 Hp after 16 consecutive grinding cycles over1200 seconds. Sample 4 demonstrates effectively no increase in thethreshold power for all of the grinding cycles demonstrating asignificantly improved operable grinding lifetime as compared to SampleC2.

Plot 604 demonstrates the grinding power of Sample 4 on the workpiece at2500 rpm and a grinding rate of 6.5 inches/min. As illustrated by plot604, Sample 4 has a initial grinding power of approximately 2.8 Hp and afinal grinding power of 1.9 Hp after 16 consecutive grinding cycles atapproximately 800 seconds. Sample 4 demonstrates effectively no increasein the threshold power for all of the grinding cycles demonstrating asignificantly improved operable grinding lifetime as compared to SampleC2.

In addition to the noted above difference in grinding performance, thebonded abrasive body of Sample 4 (plots 602 and 603) was able tocontinue grinding 40 flutes in total, which corresponds to 10 parts,before dressing. By contrast, Sample C2 was capable of grinding 16flutes total, which corresponds to 4 parts total before needingdressing. As such, Sample 4 demonstrates an improvement in grindingefficiency, as measured by parts/dress of approximately 125% over theconventional Sample C2.

Moreover, in a comparison of plots 601 and 604, it is demonstrated thatSample 4 is capable of improved grinding rate over the conventionalSample C2. Under the grinding conditions of plot 604, Sample 4demonstrated a capability to grind the same number of parts (4 total) inapproximately 700 seconds, as compared to Sample C2, which neededapproximately 1100 seconds. Accordingly, Sample 4 demonstrated animprovement in grinding time of 300 seconds, corresponding to animprovement of approximately 36% over the conventional Sample C2.Furthermore, based on the feed rate conditions for plots 601 and 604,Sample 4 demonstrated an improvement in grinding rate of 73% (usinginches/min) as compared to the conventional Sample C2. Moreover, Sample4 achieved improved grinding rates while maintaining substantially thesame grinding power, while Sample C2 demonstrated a rapid andunsatisfactory increase in grinding power.

Example 5

Sample 4 and Sample C2 are used in a flute grinding operation on aworkpiece of 0.5 inch diameter tungsten carbide with 6% cobalt. Thistype of work material is harder to grind than the workpiece of Example 4due to higher tungsten carbide content (94 vs 90%) as evidenced by thedifference between plots 701 and 702. Plot 701 represent the grindingpower for Sample C2 on a workpiece of tungsten carbide having 10% cobaltbinder at 3000 rpm and a grinding rate of 6 inches/min for a grindingtime of 800 seconds. In fact, plot 701 is the same as plot 601 of FIG.6. Plot 702 represent the grinding power for Sample C2 on a workpiece oftungsten carbide having 6% cobalt binder, at 3000 rpm and a grindingrate of 6 inches/min for a grinding time of 800 seconds. As illustrated,the power needed to grind the workpiece having 10% cobalt issignificantly less than the power needed to grind the workpiece made oftungsten carbide with only 6% cobalt for Sample C2.

By comparison, plot 703 represents the grinding power of Sample 4conducting a grinding operation on a workpiece of tungsten carbidehaving only 6% cobalt, at a speed of 2500 rpm at a grinding rate of 8inches/min for a grinding time of less than 600 seconds. As illustrated,in a comparison of plots 703 and 702, Sample 4 is capable of grinding agreater amount of the tungsten carbide workpiece at a greater rate andmore efficiently. That is, Sample 4 experiences significantly lesschange in grinding power throughout the consecutive grinding cycles ascompared to Sample C2.

In further comparison of plots 702 and 703 representing the grindingperformance of Sample 4 and Sample C2, respectively, it is noted thatSample 4 also demonstrated improvements in grinding rate. Notably, withlittle to no increase in the grinding power, Sample 4 required onlyabout 500 seconds to grind the same number of parts as required bySample C2, which required approximately 800 seconds. Accordingly, Sample4 achieved an increase in grinding rate of approximately 31% as comparedto the conventional Sample C2. Moreover, faster than the time requiredto grind the same number of parts by Sample C2.

The bonded abrasive bodies herein demonstrate compositions and grindingproperties that are distinct from conventional metal-bonded abrasivearticles. The grinding properties of the abrasive articles of theembodiments herein are more akin to vitreous bonded abrasive articlesthan state of the art metal-bonded abrasive articles. The bondedabrasive bodies of the embodiments herein demonstrate improved lifetimeof effective grinding, require significantly less dressing than otherconventional metal-bonded abrasive bodies, and have improved wearproperties as compared to state-of-the-art metal-bonded abrasive bodies.In particular, the bonded abrasive body may not require a separatedressing operation after undergoing a truing operation, which isdistinct from conditioning operations of conventional metal-bonded,bonded abrasive articles. That is, it is a typical procedure within theindustry to utilize a truing wheel in combination with a dressing stickfor resurfacing and sharpening bonded abrasive bodies utilizing metalbond materials. Accordingly, the bonded abrasive bodies of embodimentsherein are capable of grinding a greater number of parts per dress,resulting in greater efficiency and longer life as compared tostate-of-the-art metal bonded abrasive articles.

Furthermore, particular aspects of the forming process for the bondedabrasive bodies herein are thought to be responsible for certaincompositions and microstructural features. The bonded abrasive bodies ofembodiments herein include a combination of features, which may beattributed to the forming process and facilitate improved grindingperformance, including for example, an active bond composition,particular phases of the active bond composition and particularlocations of such phases, type and amount of porosity, type and amountof abrasive grains, type and amount of fillers, ratios of particulate tobond, ratios of abrasive to bond, and mechanical properties (e.g.,fracture toughness) of certain components.

In the foregoing, reference to specific embodiments and the connectionsof certain components is illustrative. It will be appreciated thatreference to components as being coupled or connected is intended todisclose either direct connection between said components or indirectconnection through one or more intervening components to carry out themethods as discussed herein. As such, the above-disclosed subject matteris to be considered illustrative, and not restrictive, and the appendedclaims are intended to cover all such modifications, enhancements, andother embodiments, which fall within the true scope of the presentinvention. Thus, to the maximum extent allowed by law, the scope of thepresent invention is to be determined by the broadest permissibleinterpretation of the following claims and their equivalents, and shallnot be restricted or limited by the foregoing detailed description.

The disclosure will not be used to interpret or limit the scope ormeaning of the claims. In addition, in the foregoing descriptionincludes various features may be grouped together or described in asingle embodiment for the purpose of streamlining the disclosure. Thisdisclosure is not to be interpreted as reflecting an intention that theclaimed embodiments require more features than are expressly recited ineach claim. Rather, as the following claims reflect, inventive subjectmatter may be directed to less than all features of any of the disclosedembodiments.

What is claimed is:
 1. An abrasive article comprising: a body comprisingabrasive grains contained within a bond material comprising a metal,wherein the body comprises a ratio of V_(P)/V_(BM) of at least about1.5, wherein V_(P) is a volume percent of particulate material includingabrasive grains and fillers within a total volume of the body and V_(BM)is a volume percent of bond material within the total volume of thebody, wherein the body comprises greater than 20 vol % porosity andwherein the bond material comprises an average fracture toughness(K_(1c)) of not greater about 4.0 MPa m^(0.5).
 2. The abrasive articleof claim 1, wherein the bond material comprises an average fracturetoughness (K_(1c)) within a range between about 0.6 MPa m^(0.5) andabout 4.0 MPa m^(0.5).
 3. The abrasive article of claim 2, wherein thebond material comprises an average fracture toughness (K_(1c)) within arange between about 0.6 MPa m^(0.5) and about 3.0 MPa m^(0.5).
 4. Theabrasive article of claim 1, wherein the ratio of V_(P)/V_(BM) is withina range between about 1.5 and about 9.0.
 5. The abrasive article ofclaim 4, wherein the ratio of V_(P)/V_(BM) is within a range betweenabout 1.7 and about 6.0.
 6. The abrasive article of claim 1, wherein thebody comprises a ratio of V_(AG)/V_(BM) of at least about 1.3, whereinV_(AG) is a volume percent of abrasive grains within the total volume ofthe body and V_(BM) is a volume percent of bond material within thetotal volume of the body.
 7. The abrasive article of claim 6, whereinthe ratio of V_(AG)/V_(BM) is within a range between about 1.3 and about9.0.
 8. The abrasive article of claim 1, wherein the body comprises anactive bond composition comprising at least 1 vol % of an active bondcomposition of the total volume of the bond material.
 9. The abrasivearticle of claim 8, wherein the active bond composition is present in anamount within a range between about 1 vol % and about 40 vol % of thetotal volume of the bond material.
 10. The abrasive article of claim 1,wherein the body comprises at least 25 vol % porosity.
 11. The abrasivearticle of claim 8, wherein the active bond composition comprises acompound selected from the group consisting of carbides, nitrides,oxides and a combination thereof.
 12. The abrasive article of claim 10,wherein the active bond composition comprises a metal element selectedfrom the group of metal elements consisting of titanium, vanadium,chromium, zirconium, hafnium, tungsten, and a combination thereof. 13.The abrasive article of claim 1, wherein a majority of the porosity isinterconnected porosity defining a network of interconnected poresextending through the volume of the body.
 14. The abrasive article ofclaim 1, wherein the bond material comprises at least one transitionmetal element.
 15. The abrasive article of claim 14, wherein the bondmaterial comprises a metal selected from the group of metals consistingof copper, tin, silver, molybdenum, zinc, tungsten, iron, nickel,antimony, and a combination thereof.
 16. The abrasive article of claim15, wherein the bond material comprises a metal alloy including copperand tin.
 17. The abrasive article of claim 1, wherein the body comprisesa bimodal distribution of abrasive grains including fine grains having afine average grit size and coarse grains having a coarse average gritsize, wherein the coarse grit size is greater than the fine average gritsize.
 18. The abrasive article of claim 1, wherein the fillers comprisea material selected from the group of materials consisting of oxides,carbides, borides, silicides, nitrides, oxynitrides, oxycarbides,silicates, graphite, silicon, inter-metallics, ceramics,hollow-ceramics, fused silica, glass, glass-ceramics, hollow glassspheres, and a combination thereof.
 19. The abrasive article of claim 1,wherein the fillers comprise a fracture toughness (K_(1c)) of notgreater than about 10 MPa m^(0.5).
 20. The abrasive article of claim 1,wherein the fillers comprise not greater than about 75 vol % of thetotal volume of the body.